1. Field of the Invention
The invention relates to sequential-access asynchronous memories, in particular, but not exclusively, asynchronous memories of the first-in first-out type (FIFO).
2. Description of the Related Art
A memory is said to be asynchronous when the incoming and outgoing data streams are gated by independent clocks.
The use of asynchronous FIFO memories in integrated circuits has many advantages, such as notably the adaptation of timing in asynchronous networks, the use of different operating frequencies within circuits, or the smoothing-out of a data stream.
Asynchronous FIFO memories, or "stacks", are already known, conventionally consisting of "overlaid" registers, where, at each cycle time, each word stored in the memory is physically tipped into the next register. As a result of all the registers working at the same time, there is substantial consumption proportional to the size of the memory.
Furthermore, the time of residence of a word in the memory is variable. Thus, it is substantial when the FIFO is of large size and almost empty, whereas it is small when the latter is almost full since an incoming word merely needs to "sit down" on the top of the stack.
Now, this difference in behaviour between a full and an empty stack may create difficulties in certain applications.
The invention aims to afford a solution to these problems.